Image of the issue: http://i.imgur.com/saGoGcK.png
As you can see, instead of displaying the text "'PLAYERS NAME' mounts 'MOUNT NAME'" in the battle log, you get a random string of something in your surroundings instead of your players name. The text could be enemies, nearby minions (your own or another players) or even other PCs and NPCs.
Been able to reproduce this just by mounting and friends can reproduce the issue as well. This was done on PC.